Closure cap with molded threads



Oct. 6 E97@ A. w. HART ETAL CLOSURE CAP WITH MOLDED THREADS 2 Sheets-Sheet l Filed Jan. 9, 1968 Oct. 6, 1970 A. W. HART ETAL 3,532,243

CLOSURE CAP WITH MOLDED THREADS Filed Jan. 9, 1968 2 Sheets-Sheet 2 WMD/2 M2M United States Patent O U.S. Cl. 21S-40 6 Claims ABSTRACT OF THE DISCLOSURE An improved threaded closure cap and method of making it and a cooperating container nish. The preferred cap has an abuse resistant shell and a liner of plastic-like material on the cap skirt having container engaging threads molded in the liner during the manufacture of the cap. A portion of the cap liner under the cap threads engages a cooperating surface on the container finish to form a barrier against insect penetration under the cap skirt. In the preferred method of forming the cap, a heat curable or uxable plastic-like material is flowed or inserted in ring-like form into the cap shell. After the material is cured or tluxed so that it has a form retaining state, the cap threads are molded into the plastic-like material.

FIELD OF THE INVENTION The present invention relates to an improved threaded closure cap and a cooperating container finish for providing an improved sealed package and to the method of forming the cap. More specifically, the present invention relates to an improved threaded cap having a metal shell together with a method of molding the cap threads and to a cooperating container finish.

SUMMARY OF THE INVENTION The closure cap of the present invention provides a threaded cap for twist off removal which at the same time incorporates an effective top seal and a side seal at the lower part of the skirt which also serves as an insect barrier. The cap and container finish are easily manufactured and the caps may be applied by existing package sealing equipment. These results have been obtained by forming the caps with a metal shell and by forming a plastic-like molded lining on the cap skirt and on the adjacent portion of the cap top. The cap threads are molded on the lining of the cap skirt. The lining also has an annular surface below the cap threads for engaging a cooperating surface on the container finish forming` a side seal and an insect barrier. The improved method of forming the cap, as more fully described below, includes a series of steps which are easily adapted to automatic cap production machinery and which include flowing or inserting a moldable liner material into the cap and then molding the cap threads in the liner material.

Accordingly, an object of the present invention is to provide an improved closure cap and cooperating container finish.

Another object of the present invention is to provide an improved abuse resistant threaded closure cap.

Another object of the present invention is to` provide an improved threaded closure cap combining an insect infestation barrier with a controlled cap removal torque.

Another object of the present invention is to provide an improved sealed package having a twist off closure and having a high degree of resistance to insect infestation.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred 3,532,243 Patented Oct. 6, 1970 r`ice to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for the purposes of illustration and description and is shown in the accompanying drawings forming a part of the specification, wherein:

FIG. 1 is a vertical sectional View illustrating a preferred embodiment of the closure cap and of the cooperating container finish prior to the application of the cap to the container;

FIG. 2 is an enlarged fragmentary vertical sectional view of a preferred embodiment of the closure cap prior to its application to a container;

FIG. 3 is a view of the cap as in FIG. 2 applied to the container of FIG. l;

FIG. 4 is a perspective view of a preferred embodiment of the closure cap partially cut away;

FIGS. 5 through 8 are diagrammatic illustrations of preferred methods of making the cap; and

FIG. 9 is a vertical sectional view of the completed cap.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE CLOSURE CAP AND CONTAINER FINISH FIG. 1 illustrates a preferred embodiment of the closure cap and container inish in accordance with the present invention. The cap 1 has a metal shell 2 including a cover portion 3 and a depending skirt 4. The skirt 4 has a preferred stepped and flared abuse resisting form, further described below, and its lower portion is provdied with a smooth edge as, for example, by forming an inwardly rolled curl 5.

As seen more clearly in FIG. 2, the metal closure shell 2 is provided with an inner lacquer coating 2a to protect the exposed portions of the metal and to improve the bond between the shell 2 and a liner 6. The lacquer may be one of the regular cap coating lacquers or it may be an organosol of the type described in U.S. Pat. No. 3,005,433 to William E. Risch and owned by the assignee of the present invention. The liner 6 is of plastic-like material and covers a substantial portion of the skirt of the cap and extends into a liner channel 7 formed by the downwardly depressed stacking panel 8 formed in the cover 3. The liner 6 has an annular sealing portion 9 adjacent the corner between the skirt 4 and the cover 3 and extending partially across the annular channel 7. Container engaging threads 10 are formed in the plasticlike liner 6 during the manufacture of the cap 1 by an improved method which will be further described below.

The preferred embodiment of the cap skirt 4 as illustrated in the drawing includes a step 11 in the upper portion of the cap skirt and a flared central portion 12 which terminates in a generally cylindrical lower portion 14 above the bead 5. This combination of the stepped portion `11 of the skirt 4 which closely follows the corresponding glass finish and the flared portion 12 provide a cap exhibiting extremely good abuse resistance to blows either on the cap top or skirt and results in the retention of a satisfactory seal and no loss of vacuum during the most severe handling which such a package would normally be subjected to in shipping, storage, and display.

The vertical portion 15 of the step 11 is also preferably slightly downwardly flared as, for example, having an angle with the vertical of about 6 and the lower portion 16 of the step slopes downwardly from the horizontal by a generally similar angle. The flared portion of the cap is particularly effective in improving its abuse resistance properties with an angle of about 15 to 20 with a preferred embodiment having an angle of about 17. The propotions illustrated in FIGS. 2 and 3 are taken from a drawing of a preferred commercial embodiment of a cap.

As seen in FIG. 3, the molded threads 10 engage corresponding glass threads or lugs 17 on the container. The cap threads 10 preferably flare downwardly a small amount to facilitate application of the closure to the container threads 17. This iiare may be of the order of a few degrees, for example, about 3 to 6.

The lower portion of the liner 6 below the threads has an inwardly facing, generally cylindrical surface 18 which cooperates with an outwardly facing annular surface 19 on the container 20 to form an insect barrier. The surface 19 is preferably on the edge of a projecting annular glass bead 21 positioned below the threads 17 on the container nish. The upper portion of the container rim comprises a sealing surface 22 for engaging the sealing portion 9 of the liner 6.

As shown in FIG. 3, the combination of the improved closure cap with the cooperating container finish forms a tightly sealed package including a seal or barrier adjacent the lower portion of the finish at bead 21. This seal protects against contamination and insect infestation between the container finish and the cap skirt and may be used to reseal the package as often as described by twisting the cap onto the container threads.

As described above, the preferred embodiment of the cap 1 has its container engaging threads molded in the plastic-like material forming the cap liner 6. A variety of elastomeric or plastomeric materials may be used for the liner and preferably these materials are chosen so that they may be applied in ring-like form in the corner between the cap cover 3 and the cap skirt 4 and so that this ring of material may thereafter be molded in place in the closure cap to assume the liner shape described above including a container top and side sealing surface and also including a side seal near the top of the finish as well as mold container engaging threads 10.

One preferred method of forming the ring is to iiow the material into the cap shell 2. A preferred material which has proven extremely satisfactory for this method is a plastisol paste which may be flowed into the corner of the cap as a paste at room temperatures and which may be thereafter heat cured and molded to the desired shape.

The plastisol liner formulations described in the above Risch Pat. No. 3,005,433 may be used with or without the fillers in the manner described in that patent. These plastisols comprise polyvinyl chloride resins with plasticizers such as dioctyl phthalate mixed together in paste form and flowable at room temperature so that they may be injected in ring-like form into the closure shells preparatory to the subsequent tiuxing and molding steps. Other plastisol formulations may also be used.

The coating for the inside of the cap preferably uses a regular primer lacquer as well as an adhesive coating which may be a regular commercial lacquer or an organosol coating applied to the plate prior to the drawing or forming of the shell 2.

In order to facilitate the control of the cap opening and closing torques a minor proportion of a torque control agent may be uniformly distribtued in the plastic material formula. A lubricant satisfactory for this purpose may comprise an acid amide of the type described in U.S. Pat. No. 3,142,401 to George I. Foss et al. and owned by the assignee of the present invention or other known 1ubricants such as silicones may be used in minor proportions suicient to obtain the removal torques desired. Such lubricants may also be applide directly to the surface of the completed cap liner as, for example, by spraying a silicone coating onto the surface of the completed liner.

In the alternative method described below where the plastic is inserted into the cap shell in the form of a precut ring, the material may comprise polyvinyl chloride or another plastic-like material which may be inserted as a ring and then shaped or molded to provide the cap threads using combined pressure and heat. Such other materials may include principal proportions of natural CII or synthetic rubber as well as polyethylene or other resins which are known to combine satisfactory sealing characteristics with an ability to be shaped or molded in place with an acceptable degree of dimensional stability.

DESCRIPTION OF THE PREFERRED METHODS OF F ORMING THE CLOSURE A preferred method of forming the cap with the molded threads formed in a iiowed-in liner is illustrated in FIGS. 5, 6 and 8. As already indicated, a preferred material for the flowed-in liner 6 is a plastic paste such as a plastisol which is flowed into the closure shell and which thereafter may be cured by being heated. The metal cap shell is formed by the usual steps by first blanking out a at disc of the proper area and by thereafter drawing this disc into a cup-like shell 2. Thereafter forming tools are used to form the inwardly rolled wire or curl 5 at the free edge of the cap skirt.

FIG, 5 illustrates the closure shell 2 having a plastisol of the type discussed above applied as a ring 6a in a suitable cap lining machine by means of a nozzle indicated at 24. The plastic is preferably flowed into the corner of the cap shell 2 so that it extends a substantial distance up the inside of the cap skirt 4 and so that it at least partially fills the annular groove 7.

In order to facilitate the handling of the closure shells 2 after the liner 6 has been flowed in, it is preferable that the shell be given a rapid preliminary heating. Here the plastisol is heated and only lightly or skin tiuxed whereupon the plastisol is in a form retaining state and iS at least lightly adhered to the cap shell 2. A heating under infrared lamps for about twenty seconds in an ambient temperature of about 200 F. provides a satisfactory skin ux. Other temperatures and times arranged to produce a partial flux may be used. This facilitates additional handling of the shell 2 without disturbing the gasket material 6.

The cap shell 2 is now subjected to a further heating step in a similar tunnel or in an electric furnace to further the fluxing of the plastisol. It has been found preferable to complete the uxing during this step so that the shell should be heated a sufficient time to completely flux the plastisol. This may be done, for example, by heating the shell in a 400 F. oven for a period of about six minutes or until the plastisol is fully fluxed.

Upon completion of the iiuxing step the cap threads 10 are formed in the linear material 6 in the area of the cap skirt 4 by placing the closure shell in a suitable holder 26 under a thread forming plunger or die 27. The die 27 is preferably cool as, for example, at room temperature while the plastisol is kept at about 400 F. as the die is pressed into the plastisol in the manner illustrated in FIG. 8 under sufficient pressure to form the cap threads 10. This combination of cool dies and a iiuxed plastisol which is held near its fiuxing temperature results in the formation of accurately dimensioned and fully set threads. The die 27 is preferably shaped as illustrated to close off the plastic in an annular zone or ring between the inner edge of the liner groove 7 and the curl 5 of the cap skirt 4. The die 27 is left in engagement with the plastisol for a sufficient period to fully form the threads 10. The die 27 is then removed from the cap 1 by relative rotation to screw the cap off the threaded plunger or by being stripped off when the compound permits.

A preferred molding method has been described above, however, where the thread dimensional stability is of lesser importance a satisfactory cap may be produced by using a heated molding die 27 so that at least the final curing or fluxing is accomplished during the molding step.

FIG. 7 illustrates a second embodiment of the method of forming thc molded liner 6 including the container engaging threads 10. In this embodiment, a pre-cut ring 28 is inserted into the shaped closure shell 2. As indicated above, the ring 28 may be polyvinyl chloride or another moldable gasket material capable of being formed into pre-cut rings of a predetermined volume and then molded in place in the shell 2. After being inserted into the shell 2, the ring 28 is shaped using a shaping die 27 in an operation similar to that illustrated in FIG. 8. Where the plastic is in the form of a ring and thus has already by iluxed or cured, the shaping or molding is preferably accomplished with cold shaping dies and with the ring 28 and shell 2 heated. Where the ring 28 is polyvinyl chloride it may also be shaped using a heating shaping die 27, i.e. a die heated, for example, to about 300 to 400 F.

The ring 28 are cut with precise dimensions and this results in the insertion of a precise volume of plastic-like material in the capshell. The precise volume gives an exact control of the molding operation which facilitates the continuous product of identical gaskets by the dies 27.

FIG. 9 illustrates the completed closure 1 including the threaded ring-like sealing liner 6 ready for application to a package of the type described above.

While the preferred embodiment of the cap, as described above, has continuous threads it is clear that other thread forms may be used and particularly that shorter threads of the type known as interrupted threads may be molded into the cap skirt for cooperation with appropriate container threads or lugs It will be seen that an improved threaded cap has been provided having threads molded into the cap liner. The cap may be turned off a package by the consumer and may be applied by the packer with easily controlled and predetermined removal torque values. This provides a cap which has a sufficiently high removal torque to remain in place during storage and shipment but which has a suiciently low removal torque for convenient removal by the consumer.

The cap liner also includes a portion which forms a barrier with the cooperating container iinish in the area of the lower edge of the cap skirt and which acts as an effective barrier against insect infestation. A sealed package is thus provided which is of particular value for food packaging including baby food packages and other products.

As various changes may be made in the form construction and arrangement of the parts herein and the particular methods described without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

Having thus described our invention, we claim:

1. A closurec ap for sealing a container comprising the combination of a shell having a top panel and a depending skirt, said skirt comprising a generally straight, downwardly flared central portion having a slight angle with the vertical, said central flared portion lying in a plane which is non-intersecting with other portions of the cap skirt, a step positioned thereabove, said step having a generally horizontal floor portion and a generally vertical wall portion, said oor portion sloping slightly downward from the horizontal and said Wall portion having a slight flare with the vertical, the downward slope of Cil the floor and the are of the wall being less than the angle with the vertical of Said central portion, a generally cylindrical lower portion below said lared central portion, said lower portion of the skirt merging directly with an inwardly rolled bead, a continuous annular lining of plastic-like material covering a major portion of said skirt and a minor portion of said top panel, said lining having a smooth annular portion adjacent the free end of the cap for forming a barrier when applied to the cooperating surface on a container, molded container threads in the portion of the lining above said smooth annular portion, and a second smooth annular portion of said lining positioned above said threads.

2. A cap as claimed in claim 1 in which said central portion has a are of about l520 with the vertical, and said wall and oor portions of said step have an angle of about 6 with the vertical and horizontal, respectively.

3. A cap as claimed in claim 1 in which said cap further comprises an annular downwardly depressed stacking panel in its central portion.

4. A sealed package comprising a closure cap having a shell with a top panel and a depending skirt, said skirt comprising a generally straight, downwardly flared central portion having a slight angle with the vertical, said central ared poition lying in a plane which is non-inter` secting with other portions of the cap skirt, a step positioned thereabove, said step having a generally horizontal floor portion and generally vertical wall portion, said oor portion sloping slightly downwardly from the horizontal, and said Wall portion having slight downward are with the vertical, said downward are being less than the are of said central portion of said skirt, a generally cylindrical lower portion below said flared central portion, said lower portion of the skirt merging directly with an inwardly rolled bead, an annular lining of plasticlike material covering a major portion of said skirt and a minor portion of said top panel, said lining having a smooth annular portion adjacent the free end of the cap skirt, a second smooth annular surface of said cap adjacent the upper end of said cap skirt, molded container engaging threads in the skirt portion of the lining between said smooth annular portions, a container having means for engaging said threads in the cap lining, and annular surfaces above and below said thread engaging means positioned for forming a barrier in combination with said smooth annular portions of the cap liner.

5. A sealed package as claimed in claim 4 in which the top comprises an annular downwardly depressed stacking panel in its central portion.

6. A sealed package as claimed in claim 4 in which the flared central portion has an angle of about 15 to 20, vertical wall portion has a ilare of about 6 from the vertical and the oor portion has slope of from about 6 with the horizontal.

References Cited UNITED STATES PATENTS 3,215,297 11/1965 Acton et al. 215--40 X DONALD F. NORTON, Primary Examiner 

